Method and apparatus for encoding a flash picture occurring in a video sequence, and for decoding corresponding data for a flash picture

ABSTRACT

When video sequences are obtained from e.g. news, interviews, conferences and sports matches, flashlight often appears in the video due to photographing. When encoding the video sequence, the intensity changes a lot so that the motion estimation can not find a well-matching block in a previous picture. Accordingly, the video encoder will encode in intra mode and thereby generate much more bits than for the neighbouring non-flash pictures. According to the invention, not the real flash picture is encoded in the video sequence but an artificial non-flash or de-flashed picture, and some indications and parameters are inserted into the bit stream to model the flash effect. The decoder can regenerate the flash picture by reconstructing the non-flash picture and then adding the flash effect. The number of bits required for coding flash pictures is thereby significantly reduced.

The invention relates to a method and to an apparatus for encoding aflash picture occurring in a video sequence, and for decodingcorresponding data for a flash picture.

BACKGROUND

Flash lighting is widely used in taking photographs. When videosequences are obtained from e.g. news, interviews, conferences andsports matches, flash light often appears in the video due tophotographing by e.g. journalists. A typical characteristic of a flashpicture is that its intensity or brightness increases abruptly so thatthe flash picture has a much stronger intensity than the previous andthe following pictures in the video sequence. Another characteristic ofa flash picture is that the intensity change is non-uniformlydistributed within the entire picture. That is, some parts of thepicture may have a greater intensity increase than other parts.Moreover, due to the different distances from the flashlight or due toshelter and the shadow, it is hard to find an accurate model forestimating the change of the intensity within the picture.

For the above two reasons, some unusual phenomena will be noticed whenthe video is encoded by existing video coding technologies, such asMPEG-2, H.263, MPEG-4 AVC/H.264 and VC-1, are based on a hybrid videocoding processing and use motion estimation to reduce the temporalredundancy. The motion estimation is block-based and tries to find thebest-matching block by determining the minimum sum of the absolutedifference (SAD) values of the residues. However, when flash happens forexample in picture P_(n) in FIG. 1, the intensity changes a lot so thatthe motion estimation can not find a well-matching block in a previouspicture P_(n−1) or P_(n−2). Accordingly, the video encoder usually tendsto encode picture P_(n) in intra mode, since in this case the intracoding can achieve a little better rate-distortion performance thancoding in inter mode. Nevertheless, no matter in which mode the blocksor macroblocks of this picture are coded, a great amount of bits will beproduced so that the whole flash picture P_(n) will usually generatemuch more bits than the neighbouring non-flash pictures P_(n−1) andP_(n+1), and this will cause a significant bit rate fluctuation fortransmission.

If only one reference frame is used, the encoding of the non-flashpicture P_(n+1) which is following the flash picture P_(n) will againmeet the same problem in that the motion estimation for the non-flashpicture P_(n+1) can not find the matched block in the flash pictureP_(n) since there is a big intensity difference between the twopictures. Consequently, again a lot of bits are generated for thenon-flash picture P_(n+1) Fortunately, the multiple reference framesprocessing feature in H.264/AVC solves this problem. The blocks ormacroblocks of non-flash picture P_(n+1) can be predicted from the othernon-flash picture P_(n−1) and hence the encoding of picture P_(n+1) willnot produce a large amount of bits. However, the multiple referenceframes still can not prevent the encoding of the flash picture P_(n)from producing too many bits.

For H.264/AVC Main and extended profiles, another approach denoted‘weighted prediction’ has been proposed by J. M. Boyce, “Weightedprediction in the H.264/MPEG AVC video coding standard”, IEEE 2004,ISCAS 2004, in order to deal with the problem of coding fade-in,fade-out, and at the same time it tries to reduce the bit rate of codinga flash picture to some extent. There are two weighted prediction modes:explicit mode, which is supported in P, SP, and B slices, and implicitmode, which is supported in B slices only. In the explicit mode,weighting factors (including multiplicative weighting factors and theadditive offsets) are transmitted in the bit stream, while in theimplicit mode the weighting factors are instead derived based onrelative distances between the current picture and the referencepictures.

INVENTION

For fade-in and fade-out, a single weighting factor and offset aresufficient to efficiently encode all the macroblocks in a picture,because the intensity change is uniformly applied across the entirepicture. But for camera flashes, the intensity change is non-uniformwithin the entire picture, therefore different macroblocks in the samepicture require different weighting factors. However, even in this waystill a lot of bits are to be used for encoding the flash picture.Typically, the number of bits wasted when encoding a flash picture isthree or more times higher than that for normal non-flash pictures underthe same quantisation parameters. Therefore, although the weightedprediction improves the coding efficiency especially in intensity orbrightness fading sequences, it can not significantly or even perfectlyreduce the bit rate burst caused by encoding a flash picture in thevideo sequence.

A problem to be solved by the invention is to reduce significantly theadditional bit rate required for coding flash pictures. This problem issolved by the methods disclosed in claims 1, 3, 5 and 7. Apparatusesthat utilise these methods are disclosed in claims 2, 4, 6 and 8.

The invention requires significantly fewer bits for coding a flashpicture whereby the subjective picture coding/decoding quality is kepton a high level. The invention is based on the human visual system HVSwhen encoding flash pictures. A flash picture is usually too transientso that the human eye does not note any details of the picture but onlythe impression of flashing. Meanwhile the HVS will complement thedetails of the flash picture in the viewing memory with that of previousand following pictures.

Based on this fact, not the real flash picture is encoded in the videosequence but an artificial non-flash or de-flashed picture, and somesimple indications and parameters are inserted into the bit stream tomodel the flash effect, i.e. an artificial picture is encoded instead ofthe real picture. Accordingly, the decoder can regenerate the flashpicture by reconstructing the non-flash picture and then adding theflash effect. In some embodiments, even the transmission of theartificial non-flash picture can be omitted, or it can be partiallycoded, and the decoder can regenerate the artificial non-flash pictureby temporal interpolation using the previous picture and the subsequentpicture.

Advantageously, the number of bits used for coding flash pictures in avideo sequence is significantly reduced and the bit rate burst occurringin known coding methods can be avoided.

The subjective impression of ‘flash picture’ is kept due to the goodexploration on the HVS. Although the decoded flash picture itself willbe a bit different from the original flash picture, people will notnotice this because they are watching the video sequence and not thesingle pictures.

In principle, the inventive method is suited for encoding a flashpicture occurring in a video sequence, wherein the encoded flash picturedata belong to a data stream representing the encoded video sequence,said method including the steps:

-   -   determining whether or not a current picture is a flash picture;    -   if not true, encoding said current picture in a normal way;    -   if true, not encoding said current picture in the normal way but        instead generating flash picture indication data and flash        picture parameters data for insertion into said data stream,        which flash picture indication data and flash picture parameters        data are to be used in decoding said data stream for generating        from an artificial non-flash picture a flash effect picture for        said flash picture,        or includes the steps:    -   if true, not encoding said current picture in the normal way but        instead generating flash picture indication data and flash        picture parameters data for insertion into said data stream and        generating an artificial non-flash picture for said flash        picture and encoding it or encoding parts thereof, which flash        picture indication data and flash picture parameters data are to        be used in decoding said data stream for generating a flash        effect picture for said flash picture.

In principle the inventive method is suited for decoding data for aflash picture that had occurred in a video sequence, wherein the encodedflash picture data belong to a data stream representing the encodedvideo sequence, and wherein said data for said flash picture wereencoded by the steps:

-   -   determining whether or not a current picture was a flash        picture;    -   if not true, said current picture was encoded in a normal way;    -   if true, said current picture was not encoded in the normal way        but instead flash picture indication data and flash picture        parameters data were generated for insertion into said data        stream,        said decoding method including the steps:    -   parsing the received data stream for getting said flash picture        indication data and said flash picture parameters data;    -   temporally interpolating from normal-way decoded pictures        adjacent to said flash picture an artificial non-flash picture        and generating therefrom a flash effect picture for said flash        picture using said indication data and flash picture parameters        data,        or:    -   if true, said current picture was not encoded in the normal way        but instead flash picture indication data and flash picture        parameters data were generated for insertion into said data        stream and an artificial non-flash picture for said flash        picture was generated and was encoded or parts thereof were        encoded,        said decoding method including the steps:    -   parsing the received data stream for getting said flash picture        indication data and said flash picture parameters data;    -   decoding or partially decoding said encoded artificial non-flash        picture;    -   generating therefrom a flash effect picture for said flash        picture using said indication data and flash picture parameters        data.

Advantageous additional embodiments of the invention are disclosed inthe respective dependent claims.

DRAWINGS

Exemplary embodiments of the invention are described with reference tothe accompanying drawings, which show in:

FIG. 1 a flash picture in a video sequence;

FIG. 2 first embodiment of flash picture encoding;

FIG. 3 second embodiment of flash picture encoding;

FIG. 4 third embodiment of flash picture encoding;

FIG. 5 fourth embodiment of flash picture encoding;

FIG. 6 flowchart for flash picture decoding;

FIG. 7 block diagram of the inventive encoder;

FIG. 8 block diagram of the inventive decoder.

EXEMPLARY EMBODIMENTS

In all embodiments, the inventive processing begins with a pre-analysisflash picture detection step or stage 10. A flash picture can bedetected easily by calculating its average intensity or its intensityhistogram and comparing it with the corresponding values of neighbouringpictures, e.g. as proposed in D. Zhang, W. Qi, H. J. Zhang, “A new shotboundary detection algorithm”, Lecture Notes in Computer Science,2195:63, 2001. If the current picture is not a flash picture, a knownvideo encoding processing 101 is carried out. If the current picture isdetermined as being a flash picture, in most of the embodiments anartificial non-flash (or de-flashed) picture is generated, a flashindication and modelling takes place, and an artificial non-flash (orde-flashed) picture is encoded.

In case a flash picture is detected, the following process is employedin the first embodiment shown in FIG. 2. In a first step or stage 21, anartificial non-flash picture is generated. Such artificial non-flashpicture can be generated in various ways, e.g. by using pictureinterpolation to construct the artificial non-flash picture P_(n) fromthe previous non-flash picture P_(n−1) and the subsequent non-flashpicture P_(n+1).

There are a lot of picture interpolation algorithms, such as the opticalflow based interpolation algorithm in J. Ribas-Corbera, J. Sklansky,“Interpolation of cinematic sequences”, IEEE Workshop on Applications ofComputer Vision, Proceedings, 1992, and motion or true motion basedinterpolation methods like described in G. Dane, T. Q. Nguyen, “Optimaltemporal interpolation filter for motion-compensated frame rate upconversion”, IEEE Transactions on Image Processing, Vol. 15, No. 4,April 2006, an in S. Sekiguchi, Y. Idehara, K. Sugimoto, K. Asai, “Alow-cost video frame-rate up conversion using compressed-domaininformation”, IEEE International Conference on Image Processing, 2005.

These known techniques have been employed in frame rate up-conversionand in error concealment. Known picture interpolation methods might havesome limitations in some cases, e.g. in the presence of high motion, butwhen these methods are used in this invention their performance can bemuch better because the information for the current picture can beobtained from the original flash picture. Therefore, when some parts ofthe current picture can not be interpolated very well from the formerand the following pictures, they can be constructed more accurately fromthe original flash picture.

Another method for artificial non-flash picture generation is using ade-flicker technology, which was originally used to reduce flickerartifacts in old movies caused by physical degradations of the film. InJ. Delon, “Movie and video scale-time equalisation application toflicker reduction”, IEEE Transactions on Image Processing, Vol. 15, No.1, January 2006, several approaches to remove flicker are described andcompared, such as an affine degradation model and histogram matching,for a scale-time equalisation.

To summarise, an artificial non-flash picture is generated by using oneof the above-cited methods or by similar processings.

In a second step or stage 22, because there is no real encoding of theflash picture, an indication (e.g. a specific code word) and parameters(for the reconstruction of a flash effect picture, e.g. intensity centrecoordinates, intensity distribution function, some coefficients of afunction to simulate the change of intensity and colour) for the currentflash picture are formed, i.e. the flash effect is model based.According to the HVS property, the human visual system will not catchthe details between the real flash picture and the model generated flashpicture when watching the video sequence. Further details of flashmodelling and parameterisation are not the focus of this invention.

In a third step or stage 23, an artificial non-flash picture accordingto these parameters is encoded (i.e. the parameters itself are alsoencoded) and the corresponding code is inserted into the video sequencebit stream. The artificial non-flash picture can be encoded using thenormal video coding methods. Much fewer bits are needed because most ofthe intensity changes due to the flashlight are removed. So there willnot be a bit rate burst in the flash picture. The subsequent non-flashpicture P_(n+1) can be predicted from this artificial non-flash picturePa_(n) or from the former non-flash picture P_(n−1).

In a second embodiment shown in FIG. 3, the step/stage 31 of forming theindication and the parameters is carried out before the step/stage 32 ofgenerating an artificial non-flash picture, which is followed by thestep/stage 33 of encoding and inserting the corresponding code into thevideo sequence bit stream.

There is another way to encode the artificial non-flash picture. Thatis, it is not coded as shown in FIG. 4 or it is partially coded as shownin FIG. 5 because it can be interpolated in the decoder from theprevious picture and the subsequent picture.

In more detail, in a third embodiment depicted in FIG. 4, merely thestep/stage 41 of forming the indication and the parameters and insertingthe corresponding code into the video sequence bit stream is present,and the artificial non-flash picture is not coded.

Sometimes the interpolation can not reconstruct the artificial non-flashpicture very well because there is some object in the picture with bigor complex motion in it. And hence, in a fourth embodiment depicted inFIG. 5, the artificial non-flash picture needs to be partially coded ina step/stage 52, following the step/stage 51 of forming the indicationand the parameters. That is, the encoder performs an interpolation firstand determines which parts of the picture can not be interpolated well.Then the encoder codes these parts (including the location and thedetail information) using the original flash picture. Similarly, in thiscondition the later non-flash picture can not predict from thisartificial picture and therefore uses the more previous pictures asreference.

Anyway, the above embodiments based on an artificial non-flash picturewill not produce as many bits as the coding of the original flashpicture.

The decoder in FIG. 6 has a step or stage 61 that parses the code forthe pictures of the received bit stream. If a non-flash picture isindicated, a known video decoding is performed in step or stage 61. If aflash picture is indicated, in step/stage 63 the current artificialnon-flash picture is decoded or, if the parameters are omitted in thebit stream, the decoder, upon receiving the indication, regenerates anartificial non-flash picture. In a following step/stage 64 the decoderadds the flash effect to the artificial non-flash picture by using thereceived and decoded parameters or, if the parameters are omitted in thebit stream, adds the flash effect to the artificial non-flash picture byusing stored default parameters.

In the third embodiment, the decoder reconstructs the missing picturePa_(n) by interpolating it from the previous decoded non-flash pictureP_(n−1) and the subsequent decoded non-flash picture P_(n+1). It is tobe noted is that in this case the subsequent non-flash picture P_(n+1)can not be predicted from the artificial picture Pa_(n) and thereforewill use the pictures before the artificial picture, e.g. P_(n−1), asreference.

In case the flash occurs in two consecutive pictures, the inventiveprocessing still works because this kind of flash can still be detectedby the above-mentioned method of D. Zhang, W. Qi, H. J. Zhang, “A newshot boundary detection algorithm”, and the two artificial non-flashpictures can still be generated according to the invention.

In FIG. 7 the encoder video data input signal IE includes macroblockdata to be encoded. In case of intraframe data without prediction asubtractor SUB simply passes the data via transform means DCT, e.g.discrete cosine transform means, and quantising means Q to entropyencoding means ECOD which may perform variable length encoding orarithmetic coding, and which deliver via encoder buffer EBUF the encodervideo data output signal OE. In case of inter predicted data or intrapredicted data, subtractor SUB subtracts predicted macroblock data PMDfrom the input signal and passes the difference data via transform meansDCT and quantising means Q to entropy encoding means ECOD. The outputsignal of Q is also fed to inverse quantising means Q_(E) ⁻¹, the outputsignal of which passes through correspondingly inverse transform meansDCT_(E) ⁻¹ to adder ADDE in the form of reconstructed macroblock orsub-macroblock difference data RMDD. The output signal of ADDE isintermediately stored in frame store and motion estimation andcompensation means FS_MC_E which include a prediction error calculatorand which also perform motion compensation on reconstructed macroblockdata or reconstructed sub-macroblock data (4*4 luma block data) andwhich deliver predicted macroblock data or predicted 4*4 luma block dataPMD to subtractor SUB and to the other input of adder ADDE. In case ofinter prediction the data intermediately stored are data related to adifferent (e.g. the previous) picture whereas in case of intraprediction the data intermediately stored are previously processed datarelated to the current input picture. Quantiser Q, inverse quantiserQ_(E) ⁻¹, and entropy encoder ECOD are controlled basically by thefilling level of an output buffer BUF. In step or stage FDT it isdetermined whether the current input picture (or two adjacent inputpictures) is a flash picture. In step or stage FE steps 21 to 23 in FIG.2, or steps 31 to 33 in FIG. 3, or steps 41 in FIG. 4, or steps 51 and52 in FIG. 5 are performed. The resulting data are either fed to entropyencoding means ECOD or to encoder buffer EBUF so that they aretransmitted in the corresponding fashion in the encoder video dataoutput signal OE.

In FIG. 8 the decoder video data input signal ID passes through decoderbuffer DBUF and entropy decoding or arithmetic decoding means EDEC,inverse quantising means Q_(D) ⁻¹, and inverse transform computing meansDCT_(D) ⁻¹, e.g. inverse discrete cosine transform means, to an adderADDD which delivers the decoder video data output signal OD. The outputsignal of ADDD is fed to frame store and motion compensation meansFS_MC_D which also perform motion compensation on reconstructedmacroblock data or reconstructed sub-macroblock data (4*4 luma blockdata) and which deliver predicted macroblock data or predicted 4*4 lumablock data PMD to the other input of adder ADDE. In case of intraframemacroblock data without prediction the adder ADDD simply passes theoutput signal of DCT_(D) ⁻¹. In case of inter predicted data the dataintermediately stored are data related to a different (e.g. theprevious) picture whereas in case of intra predicted data the dataintermediately stored are previously processed data related to thecurrent input picture. Inverse quantiser Q_(D) ⁻¹ and entropy decoderEDEC are controlled according to the kind of control for Q_(E) ⁻¹ andECOD. Normally, in motion compensation means FS_MC_D the same motionvector information is used as in motion compensation means FS_MC_E. Thetransmitted flash picture related data are regained from the receiveddata stream ID in a flash data parser step or stage FDP. in a followingflash data decoder FD steps 63 and 64 of FIG. 6 are carried out. Thereconstructed flash picture data are part of video data output signalOD.

The invention is very suitable for the application of video broadcastingor mobile related rate constrained video applications, but can also beused in connection with pre-recorded media like DVD, HD-DVD and Blu-ray.

Besides the compression of pictures with flash, the bit stream syntaxproposed in this invention can also be used for flash scene retrieval orvideo highlight detection, because in most of the cases the flashappears in the highlight scene in video sequences.

1-10. (canceled)
 11. A method for encoding a flash picture occurring ina video sequence, wherein the encoded flash picture data belong to adata stream representing the encoded video sequence, said methodcomprising the steps: determining whether or not a current picture is aflash picture; if not true, encoding said current picture in a normalway; if true, not encoding said current picture in the normal way butinstead generating flash picture indication data and flash pictureparameters data for insertion into said data stream, which flash pictureindication data and flash picture parameters data are to be used indecoding said data stream for generating from an artificial non-flashpicture a flash effect picture for said flash picture.
 12. The methodaccording to claim 11, wherein said flash picture parameters data arenot generated and included in said data stream at encoder side butdefault flash picture parameters data stored at decoder side are usedfor generating said flash effect picture.
 13. An apparatus for encodinga flash picture occurring in a video sequence, wherein the encoded flashpicture data belong to a data stream representing the encoded videosequence, said apparatus comprising: means being adapted for determiningwhether or not a current picture is a flash picture; means being adaptedfor, if not true, encoding said current picture in a normal way; meansbeing adapted for, if true, not encoding said current picture in thenormal way but instead generating flash picture indication data andflash picture parameters data for insertion into said data stream, whichflash picture indication data and flash picture parameters data are tobe used in decoding said data stream for generating from an artificialnon-flash picture a flash effect picture for said flash picture.
 14. Theapparatus according to claim 13, wherein said flash picture parametersdata are not generated and included in said data stream at encoder sidebut default flash picture parameters data stored at decoder side areused for generating said flash effect picture.
 15. A method for encodinga flash picture occurring in a video sequence, wherein the encoded flashpicture data belong to a data stream representing the encoded videosequence, said method comprising the steps: determining whether or not acurrent picture is a flash picture; if not true, encoding said currentpicture in a normal way; if true, not encoding said current picture inthe normal way but instead generating flash picture indication data andflash picture parameters data for insertion into said data stream andgenerating an artificial non-flash picture for said flash picture andencoding it or encoding parts thereof, which flash picture indicationdata and flash picture parameters data are to be used in decoding saiddata stream for generating a flash effect picture for said flashpicture.
 16. The method according to claim 15, wherein said flashpicture parameters data are not generated and included in said datastream at encoder side but default flash picture parameters data storedat decoder side are used for generating said flash effect picture. 17.An apparatus for encoding a flash picture occurring in a video sequence,wherein the encoded flash picture data belong to a data streamrepresenting the encoded video sequence, said apparatus comprising:means being adapted for determining whether or not a current picture isa flash picture; means being adapted for, if not true, encoding saidcurrent picture in a normal way; means being adapted for, if true, notencoding said current picture in the normal way but instead generatingflash picture indication data and flash picture parameters data forinsertion into said data stream and generating an artificial non-flashpicture for said flash picture and encoding it or encoding partsthereof, which flash picture indication data and flash pictureparameters data are to be used in decoding said data stream forgenerating a flash effect picture for said flash picture.
 18. Theapparatus according to claim 17, wherein said flash picture parametersdata are not generated and included in said data stream at encoder sidebut default flash picture parameters data stored at decoder side areused for generating said flash effect picture.
 19. A method for decodingdata for a flash picture that had occurred in a video sequence, whereinthe encoded flash picture data belong to a data stream representing theencoded video sequence, and wherein said data for said flash picturewere encoded by the steps: determining whether or not a current picturewas a flash picture; if not true, said current picture was encoded in anormal way; if true, said current picture was not encoded in the normalway but instead flash picture indication data and flash pictureparameters data were generated for insertion into said data stream, saiddecoding method comprising the steps: parsing the received data streamfor getting said flash picture indication data and said flash pictureparameters data; temporally interpolating from normal-way decodedpictures adjacent to said flash picture an artificial non-flash pictureand generating therefrom a flash effect picture for said flash pictureusing said indication data and flash picture parameters data.
 20. Themethod according to claim 19, wherein said flash picture parameters dataare not generated and included in said data stream at encoder side butdefault flash picture parameters data stored at decoder side are usedfor generating said flash effect picture.
 21. An apparatus for decodingdata for a flash picture that had occurred in a video sequence, whereinthe encoded flash picture data belong to a data stream representing theencoded video sequence, and wherein said data for said flash picturewere encoded by the steps: determining whether or not a current picturewas a flash picture; if not true, said current picture was encoded in anormal way; if true, said current picture was not encoded in the normalway but instead flash picture indication data and flash pictureparameters data were generated for insertion into said data stream, saidapparatus comprising: means being adapted for parsing the received datastream for getting said flash picture indication data and said flashpicture parameters data; means being adapted for temporallyinterpolating from normal-way decoded pictures adjacent to said flashpicture an artificial non-flash picture and for generating therefrom aflash effect picture for said flash picture using said indication dataand flash picture parameters data.
 22. The apparatus according to claim21, wherein said flash picture parameters data are not generated andincluded in said data stream at encoder side but default flash pictureparameters data stored at decoder side are used for generating saidflash effect picture.
 23. A method for decoding data for a flash picturethat had occurred in a video sequence, wherein the encoded flash picturedata belong to a data stream representing the encoded video sequence,and wherein said data for said flash picture were encoded by the steps:determining whether or not a current picture was a flash picture; if nottrue, said current picture was encoded in a normal way; if true, saidcurrent picture was not encoded in the normal way but instead flashpicture indication data and flash picture parameters data were generatedfor insertion into said data stream and an artificial non-flash picturefor said flash picture was generated and was encoded or parts thereofwere encoded, said decoding method comprising the steps: parsing thereceived data stream for getting said flash picture indication data andsaid flash picture parameters data; decoding or partially decoding saidencoded artificial non-flash picture; generating therefrom a flasheffect picture for said flash picture using said indication data andflash picture parameters data.
 24. The method according to claim 23,wherein said flash picture parameters data are not generated andincluded in said data stream at encoder side but default flash pictureparameters data stored at decoder side are used for generating saidflash effect picture.
 25. An apparatus for decoding data for a flashpicture that had occurred in a video sequence, wherein the encoded flashpicture data belong to a data stream representing the encoded videosequence, and wherein said data for said flash picture were encoded bythe steps: determining whether or not a current picture was a flashpicture; if not true, said current picture was encoded in a normal way;if true, said current picture was not encoded in the normal way butinstead flash picture indication data and flash picture parameters datawere generated for insertion into said data stream and an artificialnon-flash picture for said flash picture was generated and was encodedor parts thereof were encoded, said apparatus comprising: means beingadapted for parsing the received data stream for getting said flashpicture indication data and said flash picture parameters data; meansbeing adapted for decoding or partially decoding said encoded artificialnon-flash picture, and for generating therefrom a flash effect picturefor said flash picture using said indication data and flash pictureparameters data.
 26. The apparatus according to claim 25, wherein saidflash picture parameters data are not generated and included in saiddata stream at encoder side but default flash picture parameters datastored at decoder side are used for generating said flash effectpicture.
 27. A storage medium, for example an optical disc, thatcontains or stores, or has recorded on it, an encoded digital videosignal containing data for at least one flash picture that is encodedaccording to the method of claim 11.